Previously, many vehicles have been developed using hydrofoils or buoyant supports in combination with a propulsion system in the water and airfoils have long been in use for lifting airborne payloads. Hull shapes, airfoil and hydrofoil arrangements and the controls suitable for a gradual transition from buoyant to dynamic support have not been described in the prior art. This is particularly evident with an airfoil providing partial support and thrust and with the hull, including hydrofoils, also providing partial support and with the airfoils and hydrofoils supporting a gradually increasing fraction of the weight as speed increases. The combination of a water sustained hull and a warpable beam airfoil has indeed been lacking.
A search of the prior art did not disclose any patents that read directly on the claims of the instant invention, however, the following U.S. Pat. Nos. were considered related:
______________________________________ U.S. PAT. NO. INVENTOR ISSUED ______________________________________ 3,987,982 Amick 24 October 1976 3,295,487 Smith 3 January 1967 1,949,818 Tarbox 6 March 1934 1,613,890 Herreshoff 11 January 1927 1,356,300 McIntyre 19 October 1920 ______________________________________
Amick teaches a combination sailplane and a sailboat with large dihedral of the wing and tail surfaces and buoyant wing tip end plates to resist capsizing at low speeds. In the sailing mode, the leeward wing is approximately horizontal and the windward wing acts as a sail, supplying the necessary horizontal component of the air load.
Smith discloses a hydrofoil sailboard with a single diagonal sail wing. The side forces of the sail are resisted by hydrodynamic forces of the hulls centerboard, daggerboard or vertically oriented hydrofoils. In one embodiment, the sailboard contains fore and aft air rudders.
Tarbox teaches a non-planar truss member for aircraft wings with flat sheet metal parts with a portion readily joined to a longitudinal member. The truss is a combination of triangles formed with constituent cap strips and triangulated beading. Its embodiment would have only incidental torsional flexibility, however, as indicative of the state-of-the-art.
Herreshoff introduced the importance of a foil shaped sail in use on a conventional hull with a centerboard for stability. The sail had the shape of a cambered airfoil, however, it was utilized in a vertical position relative to the hull.
McIntyre disclosed a pair of hydrofoils mounted on outriggers inclined approximately 45 degrees to the vertical such that they provide lift as well as side forces. As the speed increases, the hydrofoils tend to lift the center hull out of the water.